The present invention is related to the field of magnetic resonance.
More specifically, the invention is related to medical applications of magnetic resonance, in particular with respect to veterinary applications on big animals.
Still more specifically, the invention is related to an apparatus for conducting nuclear magnetic resonance experiments on a member of the body, in particular an extremity of a big animal, comprising a magnet assembly for receiving the extremity and a radio frequency (rf) assembly for irradiating rf signals on the extremity and/or for receiving nuclear magnetic resonance signals from the extremity.
It is well-known to utilize commercially available nuclear spin tomographs for examining the ankle joints, the so-called xe2x80x9chocksxe2x80x9d of horses (http:  www.bruker.de medical tmb biospec horse index.htm of Aug. 10, 1999, 16.48 hours).
For such an examination the front leg or the rear leg of a horse must be brought into a solenoid coil of the nuclear spin tomograph, for conducting the measurements. As solenoid coils of commercially available nuclear spin tomographs have a horizontal axis, the horse for that purpose must be laid on its lateral side for introducing the front leg or the rear leg into the coil. As this is not the natural position for the horse, it is necessary to anesthetize the horse, at least to strongly sedate same. However, such manipulations on big animals, in particular on horses, are subject to substantial risks because horses react approximately five times as sensitively on anesthetics as compared to humans. Due to the inherent risks it is impossible to proceed as outlined above when extremely valuable big animals are to be examined, in particular racing horses.
U.S. Pat. No. 4,981,136 discloses a nuclear magnetic resonance apparatus for evaluating muscle efficiency and maximum power of muscle of a living animal, in particular a horse. This prior art apparatus utilizes a treadmill which is arranged such that a harnessed horse may run thereon. The treadmill extends through a very large solenoid coil. A measuring coil acting as a rf assembly for receiving signals for the nuclear resonance measurements is attached to the horse itself.
The prior art apparatus is, hence, extremely complicated and costly because a solenoid coil of about two meters inner diameter is required. Further, the mechanical components of the treadmill might cause substantial disturbances of the magnetic field. A precise examination of a specific member of the body of the horse, in particular of the horse""s hock, is impossible for the simple reason that the ankles of the horse and, hence, the hocks are continuously moved when the horse is running.
EP 0 913 122 A1 discloses an examination table for imaging nuclear resonance measurements on extremities. The examination table has a design similar to that of a gynecologic examination chair. The patient lies on the examination table with one leg being spread away and resting in an elevated position on a cushion whereas the other leg, also spread away, is introduced into the measurement opening of a nuclear spin tomograph.
This examination table is, hence, only adapted to be used for the examination on humans.
EP 0 825 450 A2 discloses an apparatus for conducting nuclear resonance measurements on extremities of a human. The apparatus comprises a small solenoid coil being designed such that e.g. a hand may be introduced therein whereas the arm from the hand joint on is positioned outside the coil. For avoiding rf interferences, the arm is shielded with some kind of cuff.
This prior art apparatus is, hence, also solely intended to be used for humans who either hold still during the examination by their own will, i.e. because they feel responsible, or because they have been slightly sedated. An examination of big animals, in particular of horses, is impossible with this prior art apparatus.
It is, therefore, an object underlying the invention to improve an apparatus of the type specified at the outset, such that examinations on big animals, in particular on horses, become possible without the need of affecting the big animal more than absolutely necessary. By doing so it shall become possible to conduct measurements on highly valuable big animals, in particular on race horses which react highly sensitively on anesthetics or sedating agents.
According to the apparatus specified at the outset, this object is achieved in that the apparatus comprises a housing adapted to the shape of the big animal, that the housing comprises a protrusion for receiving the extremity, that the protrusion is adapted to be inserted into the magnet assembly, and that the rf assembly is adapted to be attached to the protrusion.
The object underlying the invention is thus entirely solved.
For, if a housing is used that is adapted to the shape of the big animal, the big animal may be brought into the housing and needs not to be sedated or anesthetized, in any event not to a larger extent. Big animals are frequently accustomed to such housings, for example horses being accustomed to corresponding transport vehicles within which horses may be transported within the normal traffic. A horse being accustomed to such a transport vehicle will certainly also enter into a housing adapted to its shape because it is accustomed to such a surrounding.
The use of a protrusion for receiving the body member has the advantage that the body member may be utilized for a measurement in an isolated position. A horse, for example, must only place one leg in front of the other so that the front leg may be subjected to an examination. It is then only necessary to introduce the protrusion into the magnet assembly and to operate a rf assembly attached to the protrusion correspondingly in order to conduct analytical or imaging nuclear resonance measurements as known per se.
In a preferred embodiment of the inventive apparatus, the housing encloses the big animal tightly.
This measure has the advantage that the animal is to a high degree fixed within the housing. The term xe2x80x9ctightlyxe2x80x9d, however, is to be understood to mean an arrangement allowing the big animal to essentially stand still in a predetermined position, thus avoiding that measuring artifacts are generated due to big movements. Such a xe2x80x9ctightxe2x80x9d housing is well-known to the big animal, as already mentioned, namely from corresponding transport vehicles which, too, are configured relatively tightly so that the animal is not injured during traveling, in particular during starting, during braking or when driving through a bend.
In another preferred embodiment of the inventive apparatus, the housing is configured impermeable for rf signals.
This measure has the advantage, known per se, that neither the high power rf exciting radiation may irradiate into the surrounding nor that radiation, for example radiation from radio or television stations may be irradiated into the housing and interfere with the measuring result. Only excitation signals will, therefore, be irradiated within the housing and will then be received and processed as corresponding measuring signals.
In a preferred embodiment of this variant, the housing, however, is provided with windows being permeable optically and/or permeable with respect to a room air condition.
This measure has the advantage that at least a visual contact with the big animal under examination is possible. This may, for example, be achieved in that a window is provided in the housing and the window is covered with a correspondingly tight screen acting as a Faraday cage for the rf signals of interest, whereas, on the other hand, it allows a visual contact with the big animal that may be calmed down by the physical presence of its owner. Moreover, an exchange of air and temperature thus becomes possible between the interior of the relatively tight housing and the surrounding atmosphere.
Moreover, it is preferred when the housing is provided with doors.
These doors may be configured relatively large for allowing an easy access to the housing. On the other hand the doors can also be configured relatively small for allowing a tactile contact with the big animal during the examination. In this connection a corresponding flexible shielding may be provided in the area of the doors, allowing to reach into the housing with the hand or with an arm without essentially altering or affecting the rf shielding when doing so.
Further, one may in a preferred manner provide the housing with a feeding device.
This measure has the advantage that the big animal may eat during the examination and is, hence, detracted therefrom.
For most applications it is preferred that the housing is adapted to receive the big animal in an upright position.
Moreover, it is preferred when the housing is mechanically reinforced in its bottom portion and in its wall portion adjoining the bottom portion.
This measure has the advantage that damaging of the housing may be prevented in case that the big animal, for example the horse, lashes out during the examination.
In other preferred embodiments of the invention, the housing is provided with fastening means for the body members or extremities.
This measure has the advantage that, if need arises, the body member under examination, for example, a front leg or a rear leg of a horse, may be fixed during the examination. By doing so, motion artifacts are minimized.
In still another group of embodiments of the invention, the protrusion is made detachable from the housing.
This measure has the advantage that the protrusion together with the rf assembly mounted thereto may be used for examining various body members, for example the right and the left front leg or the right and the left rear leg or for examining of all legs of a horse. An examination of the head and/or the neck of the horse is also possible in this way if a correspondingly dimensioned protrusion is used together with a magnet system having an air gap that may receive the protrusion.
For that purpose it is further preferred when the protrusion is adapted to be displaced on the housing.
This measure has the advantage that, for example, the right and the left front leg (or rear leg, respectively) of a horse may be examined one after the other without requiring substantial rearrangements on the apparatus and without the necessity to mount the relatively complicated rf assembly on four protrusions.
An especially good effect is, further, achieved when the magnet assembly comprises a magnet with an open air gap and the protrusion is adapted to be brought into the air gap.
This measure has the advantage that a relatively simple magnet assembly concept may be used and that the accessibility of the area of the homogeneous magnetic field may also be ensured quite simply.
In this regard it is, further, preferred when the magnet has an iron yoke.
This measure has the advantage that the magnet may be operated relatively simply. In an iron magnet having resistive exciting coils a mobile operation is theoretically possible, provided that a sufficiently strongly dimensioned source of electric current is available. It is, therefore, possible to operate the inventive apparatus, e.g. in stables, in race courses or at other places of action outside veterinary hospitals. As an alternative, permanent magnet poles could be utilized or superconducting coils.
In this regard it is, further, preferred when the magnet is a H-magnet or a U-magnet, preferably having an offset yoke plane.
This measure has the advantage that the air gap may be accessed very easily.
This holds true, in particular, when the magnet is positioned under an angle with respect to the vertical direction.
In that case it is, namely, possible to insert the protrusion along a horizontal direction, without running the risk of a collision with the yoke.
For that purpose it is, further, preferred when the magnet is adapted to be displaced in a horizontal and/or in a vertical direction and/or when the housing is adapted to be displaced in a horizontal and/or in a vertical direction.
These measures have the advantage that, as the case may be, an optimum sequence of movements between the magnet system and the housing is possible for bringing the protrusion into the magnet system.
As already mentioned, it is particularly preferred to utilize the inventive apparatus for measurements on horses, in particular for receiving a leg of a horse and, still more specifically, for conducting measurements on ankle joints or hocks of the horse.
The invention is, however, in now way limited to this application. Moreover, it can be used for numerous other measurements on big animals, and not only on extremities thereof but also on other body members, without leaving the scope of the present invention.
More advantages become apparent from the description and the enclosed drawing.
It goes without saying that the features mentioned before and those that will be explained hereinafter, may not only be used in the particularly given combination, but also in other combinations or alone without leaving the scope of the present invention.